a. Field of the Invention
The instant invention relates to ablation electrode assemblies. The present invention further relates to ablation electrode assemblies having a mechanism for irrigating targeted areas. The present invention further relates to a thermally insulated irrigation ablation electrode assembly that includes an insulation member and/or insulation coating that thermally insulates the ablation electrode from the manifold which provides fluid irrigation and enhances the temperature response exhibited by the electrode assembly.
b. Background Art
Electrophysiology catheters have been used for an ever-growing number of procedures. For example, catheters have been used for diagnostic, therapeutic, and ablative procedures, to name just a few examples. Typically, a catheter is manipulated through the patient's vasculature and to the intended site, for example, a site within the patient's heart, and carries one or more electrodes, which may be used for ablation, diagnosis, or other treatments.
There are a number of methods used for ablation of desired areas, including for example, radiofrequency (RF) ablation. RF ablation is accomplished by transmission of radiofrequency energy to a desired target area through an electrode assembly to ablate tissue at the target site. Because RF ablation may generate significant heat, which if not controlled can result in excessive tissue damage, such as steam pop, tissue charring, and the like, it is desirable to include a mechanism to irrigate the target area and the device with biocompatible fluids, such as saline solution. The use of irrigated ablation catheters can also prevent the formation of soft thrombus and/or blood coagulation.
Typically, there are two classes of irrigated electrode catheters, open and closed irrigation catheters. Closed ablation catheters usually circulate a cooling fluid within the inner cavity of the electrode. Open ablation catheters typically deliver the cooling fluid through open outlets or openings on the surface of the electrode. Open ablation catheters use the inner cavity of the electrode, or distal member, as a manifold to distribute saline solution, or other irrigation fluids known to those skilled in the art, to one or more passageways that lead to openings/outlets provided on the surface of the electrode. The saline thus flows directly through the outlets of the passageways onto the distal electrode member. This direct flow of fluid through the distal electrode tip lowers the temperature of the distal tip during operation, rendering accurate monitoring and control of the ablative process more difficult. Accordingly, it is desirable to have a method that allows for cooling of the electrode while having accurate monitoring and control of the ablative process. In addition, due to the heat created by the ablation procedures and the direct contact of the irrigation member with the ablation electrode, the irrigation channels may have a tendency to overheat if the manifold is made of metal or any other thermally conductive material. As a result, the manifold or irrigation member has generally been made of a reduced thermally conductive material, such as for example, plastic or any other plastic-like material. Although the reduced thermally conductive manifold may be beneficial, plastic-like manifolds or irrigation members are generally difficult to machine in the proportions necessary for the use in catheter assemblies and the resulting structures may cause reliability issues. Moreover, a major drawback of an irrigation catheter is its lack of temperature response due to the fluid cooling of the ablation electrode.
Overall, open flush irrigated ablation catheters may improve the safety of RF catheter ablation by preventing protein aggregation and blood coagulation. In addition, in order to improve and/or maximize the effect of irrigation, it important to ensure that the irrigation fluid is able to effectively cool the electrode assembly, in particular, the ablation electrode, while at the same time effectively controlling the temperature response of the ablation electrode.